1. Field of the Invention
The subject invention relates to a passively activated safety shield for a needle, such as the needle for an IV infusion set, a blood collection set or a fluid collection tube holder.
2. Description of the Related Art
A prior art blood collection set or IV infusion set includes a needle cannula having a proximal end, a pointed distal end and a lumen extending between the ends. The proximal end of the needle cannula is securely mounted in a plastic hub with a central passage that communicates with the lumen through the needle cannula. Thin flexible thermoplastic tubing is connected to the hub and communicates with the lumen of the needle cannula. The end of the tubing remote from the needle cannula may include a fixture for connecting the needle cannula to a blood collection tube or some other receptacle. The specific construction of the fixture will depend upon the characteristics of the receptacle to which the fixture will be connected.
Some fluid collection procedures employ a rigid blood collection holder instead of the above-described blood collection set. The tube holder includes a proximal end, a distal end and a tubular side wall extending between the ends. The proximal end of the holder is widely open and defines an entrance to a tube receptacle within the tubular side wall. A distal end wall extends partly across the distal end of the holder and has a mounting aperture that communicates with the tube receptacle. The mounting aperture in the distal end wall may include internal threads, movable jaws or similar structure for releasably receiving a needle assembly. The needle assembly includes a rigid plastic hub configured for releasable engagement with structure at the mounting aperture in the distal end wall of the holder. The needle assembly further includes a non-patient cannula that extends proximally from the hub and an IV cannula that extends distally from the hub. The non-patient cannula typically is covered by an elastomeric multiple sample sleeve and projects into the receptacle of the holder when the hub of the needle assembly is engaged with the threads or other structure at the mounting aperture in the distal end wall of the tube holder. The proximally extending non-patient cannula and the distally extending IV cannula typically are covered by separate packaging covers prior to use.
The needle assembly, tube holder and evacuated tube are employed by first removing the packaging cover over the non-patient cannula and engaging the hub in the mounting aperture in the distal end wall of the tube holder. Thus, the non-patient cannula projects into the holder. The packaging shield over the IV cannula then is removed and the pointed distal end of the IV cannula is used to access a blood vessel or other source of bodily fluid to be tested. The evacuated tube then is urged into the open proximal end of the holder so that the non-patient cannula pierces the rubber closure of the evacuated tube. The pressure differential will cause blood or other bodily fluid to flow into the evacuated tube. The evacuated tube will be separated from the needle holder after sufficient blood or other bodily fluid has been collected. Additional evacuated tubes then can be inserted into the holder for collecting further samples. The IV cannula is withdrawn from the patient after a sufficient number of samples have been collected.
Accidental sticks with a needle are painful and can lead to infection. Additionally, an accidental stick with a used needle can transmit disease. Accordingly, most prior art needle assemblies are provided with some form of shield to minimize the risk of an accidental needle stick. For example, prior art needle assemblies typically are provided with a packaging cover mounted over the needle cannula prior to use. The prior art packaging cover is frictionally engaged with the needle hub and can be removed immediately prior to using the needle assembly. Reshielding the used needle cannula with the original packaging cover would require the medical practitioner to hold the needle assembly in one hand and to move the point of the used needle cannula toward the hand in which the packaging cover is held. This reshielding procedure can lead to the accidental needle stick that the medical practitioner is trying to avoid. Accordingly, manufacturers of needle assemblies discourage medical practitioners from reshielding the used needle cannula with the original packaging cover.
Most prior art needle assemblies include a safety shield that can be moved into shielding engagement with a used needle cannula without risking an accidental needle stick. For example, some prior art needle assemblies include a needle shield hingedly connected to the needle hub. The hinged shield initially may be in a position that is spaced angularly from the needle cannula. However, the shield can be rotated relative to the needle hub and into shielding engagement around the used needle cannula. Digital forces for rotating this prior art hinged safety shield typically can be applied at a location near the needle hub and spaced from the pointed end of the needle cannula. As a result, shielding can be carried out manually without placing a hand near the point of the used needle cannula.
Other prior art safety shields include a rigid tubular member that is telescoped over the needle hub and/or over any medical device to which the needle assembly is mounted. The rigid safety shield can be moved from a proximal position where the needle cannula is exposed, into a distal position where the safety shield surrounds the used needle cannula. This shielding operation typically can be completed without placing a hand near the tip of the used needle cannula.
Some needle shields are referred to as tip guards, and include a small rigid guard that can be telescoped along the length of a needle cannula. The prior art tip guard may include some form of tether for limiting the travel of the tip guard to the length of the needle cannula. Additionally, the prior art tip guard typically includes structure that lockingly engages over the tip of the used needle cannula to prevent a re-exposure. The structure for preventing re-exposure may include a metallic spring clip or a transverse wall integrally formed with one end of the tip guard.
Some prior art needle assemblies are provided with metallic coil springs between the needle hub and the safety shield. A latch typically is provided for retaining the spring in a compressed state prior to and during use of the needle cannula. The latch is released upon removal of the needle cannula from the patient, and the spring then drives the shield distally and into shielding engagement with the needle cannula. Needle cannulas for blood collection sets and IV infusion sets typically are very small. Accordingly, the latches and the springs also must be very small. As a result, it often is difficult to access and release the latch. Furthermore, there is a significant potential for unreliable performance of the very small coil spring that had been stored in a compressed state for a long time.
All of the above described prior art shields for used needle cannulas require direct manual activation by the medical practitioner. The practitioner, however, often has many simultaneous responsibilities in the hectic environment of a health care facility. Thus, the used needle cannula may be withdrawn from a patient and deposited on a nearby surface with the intention of completing the shielding at a more convenient time. However, the exposed used needle cannula creates a substantial risk prior to completion of the shielding. Furthermore, there are many occasions where the needle of a blood collection set or an IV infusion set is pulled out, intentionally or unintentionally, by a patient. In this situation, shielding will not have been attempted, and the used needle cannula will remain exposed. In still other instances, the medical practitioner will inadvertently drop the used needle cannula immediately after withdrawal from the patient or during a shielding attempt. The immediate reaction of many medical practitioners will be to reach quickly for the falling needle cannula. This attempt to retrieve the falling needle cannula creates a significant possibility for an accidental needle stick.
In view of the above, it is an object of the subject invention to provide a passively shieldable needle assembly that will achieve secure shielding of a used needle cannula automatically upon removal of the needle cannula from the patient.